Digital printing apparatus, particularly digital printing apparatus of on-demand inkjet printing, has gained rapid development nowadays. The main imaging principle of the digital printing apparatus of on-demand inkjet printing is that, when a carrier (e.g., paper) reaches a predetermined position, a piezoelectric crystal comprised in an imaging component nozzle extrudes ink in response to a pulse signal output from an encoder, and ejects ink droplets onto a surface of the carrier for imaging.
Different application scenarios have different requirements on the resolution of an image printed by the digital printing apparatus of on-demand inkjet printing. Since a lateral resolution of the printed image is decided by a physical position of the imaging component nozzle, the lateral resolution of the printed image is fixed; a longitudinal resolution of the printed image is decided by a frequency of the pulse signal output from the encoder, that is, if the pulse signal output from the encoder has a different frequency, the printed image has a different longitudinal resolution; once the model of the encoder is fixed, the frequency of the pulse signal output from the encoder is fixed, hence the longitudinal resolution of the printed image is also fixed.
Conventionally, a flexible configuration of the longitudinal resolution of the printed image is achieved by performing frequency-division or frequency-multiplication processing on the pulse signal output from the encoder. The frequency-division value and frequency-multiplication value corresponding to the longitudinal resolution are determined according to the determined longitudinal resolution of the printed image; the pulse signal output from the encoder is frequency-multiplied according to the frequency-multiplication value corresponding to the longitudinal resolution; and the frequency-multiplied signal is frequency-divided according to the frequency-division value corresponding to the longitudinal resolution. Since there is the possibility that extra clock cycles exist during the frequency-multiplication processing, which leads to an uneven distribution of the periods of a plurality of frequency-multiplied pulse signals, this results in an uneven distribution of the periods of a plurality of frequency-divided pulse signals, and uneven pulse signals applied to the piezoelectric crystal comprised in the imaging component nozzle, so that a poor quality of the printed image results.
To sum up, at present, the method of frequency-dividing and frequency-multiplying the pulse signal output from the encoder is used to flexibly configure the longitudinal resolution of the printed image, however, the printed image has poor quality.
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